Droséra

The will droséras or rossolis is small Plantes carnivores of the family of the Droséracées, pertaining to the kind Drosera .

There exist 80 to 110 S of Drosera located mainly in the southern hemisphere. One finds half of these species in the south-west of Australia.

There exists in Europe three species of Drosera. All present a rivet washer of coloured sheets. Often these species not very visible on bottom of are éricacées dark or of reddish Sphaigne S. Most cosmopolitan is Drosera rotundifolia , which has the sheets applied against the ground, whose limb is round. The two other species have the lengthened and more or less drawn up sheets. All the species live on wet, poor and acid grounds, generally in Marais, wet Lande S or Tourbière S acids of the Northern hemisphere, often in colony of many individuals, slightly enracinées in the middle of the sphaignes. In France where they are protected one finds some in particular in the Natural park of the Vosges of North.

Description

The Limbe is orbicular. The Sheet S, in the case of Drosera rotundifolia , make approximately 3 to 5 cm length. They are sensitive to the mechanical and chemical excitations. They carry glanduleux hairs, sometimes irritable, secreting mucilagineuses substances which attract and lime the Insectes. After the capture, the hairs bend towards the limb of the sheet. The insects thus trapped can then be digested by proteolytic Enzymes.
Les Fleur S is blanchâtres laid out out of ear releases and stalk at the end of a pole from 6 to 20 cm in height drawn up as of the base, in the shape of stick and seldom oarswoman at the top. The flower has 5 Sépale S, 5 Pétale S, 5 cheesecloth S and 3 Carpelle S. a large floral pole makes it possible not to trap the pollinating insect. The Fruit is a capsule containing of the albumenized, thread-like and winged Graine S with the two extremities. The genetic material set out again on 80 Chromosome S.

Operation of the trap

Will droséras are equipped with a semi-active trap. Indeed, this one has a mechanical action but which is secondary and of low amplitude. Will droseras probably have mechanisms of attraction of the insects. The studies made on these mechanisms never could show the use of Phéromone S by will droséras. It would seem that will droséras them use in priority the direction of the sight of the animals. It is noted that the sun, the liquid makes it possible the sheet to shine as if they were covered with dew or nectar. Its secretions are increasingly abundant with the duration of the jeun.

Each sheet comprises a face of adhesive hairs. Each one of these hairs is finished by a hat, is composed of several secreting mucilage cells or enzymes, carried by a pluricellular and vascularized foot.

More precisely, the pedicel of each Tentacule includes/understands one or two files of spiral vessels surrounded by some bases of parenchymatous cells . The vessels end, in the reinflated part of the tentacle, with a solid mass of also spiral vascular elements but much shorter, solid mass covered with secreting cells. These cells work out Mucilage S and Enzyme S proteolytic S. secretions of the tentacles of will droséras are acid, supporting the action of the proteolytic enzymes. A protease with peptonizing action was extracted from secretions. Secretion is carried out through parenchymatous cells of the tentacular pedicels which contain, to at-rest state, large a Vacuole containing in solution a Pigment anthocyanic bright red coloring these tentacles.

The strategy of capture of the prey is of type “ flypaper ”. The prey coming to be posed on one of these sheets, is retained there by the viscous matter of the tentacles. Then its own activity puts it more and more in contact with the lime of the hairs. Its agitation to emerge stimulates the activity of the secreting cells. Then, the tentacles and the limb of the sheet are put moving very slowly. At several hours are necessary to the complete fold of the sheet. The prey, limed, dies of asphyxiation and is finally digested. In fact this movement is used on the one hand to avoid a loss of nutritive liquid at the time of the Digestion and on the other hand to accelerate the process by supporting the maintenance of the prey and by increasing surface for the action of the digestive liquid. The latter is directed towards the center of the sheet where are located the digestive glands. In the case of the catch of an insect (the most frequent case), there does not remain any more after one or two days, in the middle of the sheet, but the skeleton Chitine ux of the animal. The sheet will put one or two weeks to regain its initial shape. The movements of the sheet of will droséras are in fact the sum of Tropisme and Nastie. During digestion, the large vacuoles anthocyanic rich person in pigment are split up by the Cytoplasme. This one, soaking at the expense of the vacuolar Colloid S, inflates and produced many Pseudopode S interns which penetrates in the vacuole, are anastomosed there, then end up dividing the latter into a great number of small dense, globulous or filamentous elements. The color of the vacuole transfers with the purplished gray. One interprets these facts like translating the passage, through these cells, of the products of proteolytic digestion. If one noted the presence (exceptional) of Bactérie S commensales which takes part in digestion, a normal digestion is also noted in the sterile liquid extracted the tentacles. Will droséras can thus digest their preys thanks to their only secretions, without symbiotic bacteria as that was thought a long time.

Historical experiments

Charles Darwin and his Francis son, carried out experiments of digestion by will droséras in 1877. They noted in particular that the nourished specimens reached a size more imposing than the others. The plants reacted well with the raw or roast meat, cheese, sausage, the egg white and milk, but refused to digest sugar, the starch and the vegetable fats.

Systematic classification

Three sub-genera and eleven sections in this kind:

Drosera

Drosera section

Drosera longifolia or Drosera anglica - Rossolis of England

Drosera intermedia - intermediate Droséra
Drosera rotundifolia - Droséra with round sheets
Drosera bequaertii
Drosera filiformis
Drosera linearis
Drosera affinis
Drosera alba
Drosera arcturi
Drosera arenicola
Drosera capensis
Drosera aliciae
Drosera spatulata
Drosera adelae
Drosera proliferated
Drosera will schizandra
Drosera will biflora
Drosera brevifolia
Drosera burkeana
Drosera neocaledonia

Bryastrum section

Drosera nitidula

Drosera dichrosepala
Drosera barbigera
Drosera ericksoniae
Drosera pulchella
Drosera pygmaea
Drosera scorpioides
Drosera androsacea

Coelophylla section

Drosera glanduligera

Lasiocephala section

Drosera petiolaris

Drosera falconeri
Drosera paradoxa
Drosera banksii
Drosera brevicornis
Drosera broomensis
Drosera caduca

Meristocaules section

Drosera meristocaulis

Phycopsis section

Drosera binata

Ptycnostigma section

Drosera acaulis

Thelocalyx section

Drosera burmanii

Ergaleium

Ergaleium section

Drosera bulbigena

Drosera peltata
Drosera andersoniana

Erythrorhizae section

Drosera erythrorhiza

Drosera macrophylla
Drosera browniana
Drosera bulbosa

Stoloniferae section

Drosera stolonifera

Regiae

Drosera regia

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